(1) Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and a printer used in an electrophotographic method, and particularly, to an image forming apparatus with a detachable imaging cartridge.
(2) Description of the Related Art
An image forming apparatus with a detachable imaging cartridge enclosing a photosensitive material, an electrostatic charging device, a developing device, and a cleaner is described for example in U.S. Pat. No. 3,985,436. Such a detachable imaging cartridge facilitates replacement of these parts when they are deteriorated with use, and development in a different color. With such a construction, however, the photosensitive material is susceptible to light exposure at the removal of the imaging cartridge when it does not enclose a charging device for transferring a toner image on the photosensitive material onto a copy sheet, which results in damage to and deterioration of the photosensitive material.
U.S. Pat. No. 4,831,407 therefore discloses an imaging cartridge enclosing the charging device so that it protects the photosensitive material from light exposure. In addition, the charging device hingedly mounted to the imaging cartridge enables easy clearance of jammed copy sheets. However, inconvenience in handling due to its protrusive form makes it unfavorable to practical use. Moreover, the charging device is not separable from the imaging cartridge.
Japanese Laid-open Utility Model No. 63-4562 discloses an imaging cartridge enclosing a charging roller. The charging roller is designed so that it contacts to the photosensitive material only when the image transfer occurs. However, neither separability of the charging roller from the imaging cartridge nor a cleaner for the charging roller is disclosed therein.